The present invention relates to ovens for preparing food and in particular to an oven that may be automatically switched between “closed-system” operation with moisture substantially sealed within the cooking volume and “open-system” operation with moisture vented out of the cooking volume.
High-end commercial ovens may provide for closed-system operation in which the oven volume is substantially sealed to retain heat and moisture and provide energy savings. Such closed-system operation is particularly desirable for “combination ovens” that may cook food using steam and fan driven (forced convection) hot air but is also useful in convection ovens (without steam) and rotisserie ovens.
In closed-system ovens, expanding steam and air is vented so that the cooking process is performed without significant pressurization. This venting may occur through a condenser where the steam is cooled before exiting to the outside air, reducing the heating and humidification of the kitchen environment. In one common condenser design, the steam is passed through a water bath which cools and condenses the steam. The temperature of the water bath is monitored and fresh, cool water is introduced into the water bath as the temperature rises. Excess water from the bath passes through an overflow into the building drain system.
Closed-system operation may be undesirable for the preparation of some foods, for example bread items where a crisp crust is desired. In such cases, open-system operation may be approximated, for example, by opening the oven door by a small amount during cooking to allow the exchange of steam and exterior air. This approach wastes energy, produces undesirable venting of steam and heat into the food preparation area, and may promote uneven cooking. Increased venting of a closed-system oven may also be obtained by manually bypassing or disabling the condenser.